Upgrading of paraffinic gasoline blending components by cyclization with a platinum/magnesium oxide alumina matrix catalyst

ABSTRACT

The octane number of paraffinic gasoline blending components may be increased by (1) cyclizing the n-paraffins with hydrogen under reforming conditions in the presence of a catalyst prepared by depositing a noble metal on magnesium oxide and mixing the resulting noble metal-magnesia into an alumina gel matrix, and (2) subjecting the cyclized component to conventional catalytic reforming.

United States Patent [191 Wilson et al.

[73] Assignee: Texaco Inc., New York, NY.

221 Filed: Jan. 21, 1974 [21] Appl. No.: 435,363

[52] US. Cl. 208/65 [51] Int. Cl. C10G 39/00 [58] Field of Search 208/65, 138, 139; 252/441,

[56] References Cited UNITED STATES PATENTS 2,602,772 7/1952 Haensel 208/139 2,651,598 9/1953 Ciapetta 208/138 [4 1 Dec. 16,1975

2,905,624 9/1959 Gleim 208/89 2,972,644 2/1961 Holmes et a1. 252/466 PT 3,395,094 7/1968 Weisz 1 208/139 3,424,669 l/l969 Carter et al.. 208/65 3,436,335 4/1969 Maziuk 208/65 3,455,813 7/1969 Hovestreydt et a1.... 208/138 3,554,902 l/197l Buss 208/139 3,558,479 l/197l Jacobson et al. 208/139 3,846,281 11/1974 Mertzweiller 208/139 Primary Examiner-Delbert E. Gantz Assistant ExaminerJames W. Hellwege Attorney, Agent, or FirmT. H. Whaley; C. G. Ries; George J. Darsa 57 ABSTRACT Theoctane number of paraffinic gasoline blending components may be increased by (1) cyclizing the nparaffins with hydrogen under reforming conditions in the presence of a catalyst prepared by depositing a noble metal on magnesium oxide and mixing the resulting noble metal-magnesia into an alumina gel matrix, and (2) subjecting the cyclized component to conventional catalytic reforming.

Claims, N0 Drawings UPGRADING OF PARAFFINIC GASOLINE BLENDING COMPONENTS BY CYCLIZATION WITH A PLATINUM/MAGNESIUM OXIDE ALUMINA MATRIX CATALYST BACKGROUND OF THE INVENTION Reforming operations, where hydrocarbon fractions such as naphthas, raffinates and condensates, are treated to improve octane numbers are well known in the petroleum processing art. One of the principal results of reforming operation is the raising of octane numbers, particularly for use in lead free gasolines. The hydrocarbon fractions which are improved by the reforming operation are composed predominantly of normal and slightly branched paraffinic hydrocarbons and naphthenic hydrocarbons together with small amounts of aromatic hydrocarbons. During reforming, a multitude of reactions take place, including isomerization, aromatization, dehydrogenation, cyclization, etc., to yield a product having an increased content of aromatics and highly branched paraffins. Thus, in the reforming operation, it is desired to dehydrogenate the naphthenic hydrocarbons to produce aromatics, to cyclize the straight chain paraffinic hydrocarbons to form aromatics, and to isomerize the normal and slightly branched paraffins to yield highly branched chain paraffins. Additionally, under the appropriate circumstances, it is also desired to effect a controlled type of cracking which is both selective in quality and quantity; i.e., the cracked paraffinic products desirably have six or more carbon atoms.

Normal and slightly branched chain paraffinic hydrocarbons of the type contained in reforming feedstock fractions have relatively low octane ratings. Highly branched chain paraffinic hydrocarbons, on the other hand, are characterized by high octane ratings. Thus, one objective of the reforming operation is to effect isomerization of the normal and slightly branched chain paraffins to more highly branched chain paraffins. Also, since aromatic hydrocarbons have much higher octane ratings than naphthenic hydrocarbons, it is also an objective of reforming simultaneously to produce aromatics in good yield. The production of aromatic hydrocarbons during reforming is effected by dehydrogenation of the naphthenic hydrocarbons and dehydrocyclization of the paraffinic hydrocarbons. Aromatic hydrocarbons are also produced by isomerization of alkyl cyclopentanes to cyclohexanes, which thereafter undergo dehydrogenation to form the desired aromatics. A convenient measure of the effectiveness of a reforming operation is based on a yield-octane relationship. It is desired in reforming to maximize this relationship, i.e., high depentanized yields for any given octane Certain hydrocarbon fractions which fall within the boiling point range for gasoline blending components are composed principally of normal and slightly branched chain paraffins. These paraffinic stocks are very low in octane number and therefore, unless they are subjected to a reforming operation, they are not suitable for inclusion in lead free gasolines. Reforming of these blending components, however, has been somewhat less than satisfactory, owing principally to undesired cracking reactions which occur in conventional reforming operations. This cracking, which produces mainly butanes and lighter hydrocarbons, results in a significant loss of gasoline product.

It is therefore a principal object of this invention to develop a method for reforming paraffinic gasoline blending components in order to increase their octane number.

It is another object of this invention to develop a method for reforming these gasoline blending components without encountering a substantial loss in product volume as a result of conversions to butanes and lighter hydrocarbons.

A further object of this invention is to develop an effective catalyst for the upgrading of highly paraffinic gasoline blending components.

SUMMARY OF THE INVENTION According to this invention, paraffinic gasoline blending components are upgraded by a two step process involving (1) cyclization of paraffins, and (2) catalytic reforming of the cyclized product in the usual manner. The cyclization step is accomplished by contacting the paraffinc gasoline blending component with hydrogen in the presence of a novel catalyst prepared by depositing a noble metal on magnesium oxide and then mixing this noble metal-magnesia into an alumina matrix.

DISCUSSION OF THE PRIOR ART Most of the multi-step reforming processes hereto fore known disclose that the cyclization reactions take place in the final, rather than the initial stages of the reforming process. The instant invention is characterized by the fact that the cyclization reactions take place prior to the other reforming reactions, e.g., dehydrogenation and isomerization. It is further characterized by the use of a novel catalyst.

US. Pat. No. 3,395,094, issued to Weisz, discloses catalyts which are typically used in multi-step reforming operations. A two step operation is disclosed in which the catalyst of the first step is platinum or another noble metal deposited on alumina. Combined with the alumina, there may be other components such as magnesium oxide. There is no indication, however, in this patent or in other prior art relating to similar reforming catalysts that the noble metal should first be deposited on magnesium oxide alone and that the magnesium oxide-noble metal mixture then be deposited on or mixed with alumina.

US. Pat. No. 3,654,184, issued to McCallister et al, discloses a platinum/germanium oxide/alumina gel catalyst. A soluble platinum compound is combined with an aqueous solution of germanium oxide. A halogenated alumina gel is then impregnated with the combined solution. The disclosure is specific to the use of a germanium oxide solution; there is no indication that magnesium or any other metal may be used in place of the germanium and, further, there is no indication that the platinum may be deposited on a solid chemical rather than being mixed with a solution.

DETAILED DISCLOSURE OF THE INVENTION The paraflinic gasoline blending component which constitutes the feedstock in the process of the instant invention is typically a hydrocarbon fraction boiling within the gasoline boiling range and having a paraffin content of from about percent or higher, most of the paraffins being in straight chain or slightly branched compounds. Examples of suitable feedstocks are light straight run naphthas, raffinates and condensates. The paraffinic stock is cyclized by contacting with hydrogen under reforming conditionswith the novel catalyst of noble metal on magnesium oxide and then mixing the resultant intermediate into an alumina matrix. The noble metal is, for example, palladium or platinum, with platinum being preferred. The deposition of the noble metal on the magnesium oxide is conveniently accomplished by impregnating magnesium oxide powder with a solution of the noble metal compound. Examples of such compounds include platinum chloride, chloroplatinic acid, ammonium chloroplatinate, dinitrodiamino platinum, palladium chloride, chloropalladic acid, and the like. When the noble metal is platinum, the preferred soluble platinum compound is chloroplatinic acid.

Additionally, the noble metal may be stabilized with a suitable metal selected from Groups IVA, VB, VIB, VIIB or VIII of the Periodic Table. Examples of such metals are: Group IVA: Ge, Sn, Pb; Group VB: V, Nb, Ta; Group VIB: Cr, Mo, W; Group VIIB: Mn, Re; Group VIII: Fe, Ni, Co, Ru, Rh, Pd, Os, Ir and Pt. (Preferred metals are underlined.)

The magnesium oxide with the noble metal deposited on or impregnated is then, if necessary, dried prior to further processing. The dried impregnated magnesium powder is then mixed with an alumina gel which may contain up to about 2% silica. The alumina gel itself is prepared by methods well known in the art, for example, by dissolving aluminum sulfate in water and then adding concentrated ammonium hydroxide in order to precipitate aluminum hydroxide.

The cyclization step may take place under ordinary reforming conditions in a reactor normally used for reforming operations. The general and preferred operating conditions for this reaction are listed below in Table I.

This reaction cyclizes the paraffms into naphthenes and aromatics in very high depentanized yields. The cyclized paraffinic stock is then passed to a conventional catalytic reforming unit containing a conventional platinum or platinum bi-metalliz reforming catalyst on an alumina or alumina containing support. This second step is run according to methods well known in the art.

SPECIFIC EXAMPLES The invention will be better understood by reference to the following specific examples which are included here for the purposes of illustration only and are not intended as limitations.

EXAMPLE I Catalyst preparation The catalyst of this example consists essentially of platinum (0.75 wt. impregnated magnesia powder in an alumina gel matrix.

MgO powder, 450 grams, was impregnated with ml. of a chloroplatinic acid solution (0.05g Pt/cc, diluted to 200cc). The platinum impregnated magnesia powder was dried on the steam plate' at a temperature of 130-140F.

The alumina gel was prepared by dissolving 490 grams of Al (SO 'l8 H O in 5 liters of distilled water to which 300cc of concentrated NI-I OI-I was added to effect precipitation of Al(OI-I) The alumina gel was washed 3 times with cold water and filtered to remove most of the sulfate. The Pt-MgO powder was then mixed with the alumina gel and passed through a C01- loid Mill. This material was dried on the steam plate for a sufficient amount of time to remove moisture and obtain a good extrusion mix. The dried material was crushed using a mortar and pestle and sieved to 40 mesh.

The material was then extruded in a California Pellet Mill in the form of l/l6 inch pellets. The pellets were dried in air on the steam plate (l30-140F.) for 8 hours at 300F. in an oven followed by calcination for 2 hrs. at 1000F. starting at 500F. and raising the temperature F. per hour. The average crush strength of the pellets was 8.0 pounds.

EXAMPLE II In this Example, the catalyst prepared in Example I was used to cyclize a Udex raffinate. The raffinate was treated in three separate runs at temperatures of 850, 900 and 950F. For all runs, pressure was 50 psig, hydrogen rate was 6,000 SCFB and the liquid hourly space velocity was 1.0. Liquid hourly space velocity (LI-ISV) is defined as the volume of liquid hydrocarbon charge per hour per volume of catalyst contained in the reaction zone. The product formed and their properties are 'set forth in the following Table II, which also sets forth the properties of the charge stock.

EXAMPLE 111 In this example, the product produced at 850F. in Example 11 and the raw raffinate charge stock were processed separately over a platinum on alumina catalyst in a conventional reforming operation. The characteristics of the catalyst used are as follows:

TABLE [11 Cl 0.23 wt.%

'y-alumina Pt 0.375 wtfic support This conventional operation was carried out at 500 psig, 1.0 LHSV, 890F. and at a hydrogen to hydrocarbon mol ratio of 6:1. The products produced from these two reforming operations and their properties are indicated in Table IV.

TABLE IV affin content of from about 70 percent or higher which comprises the steps of l cyclizing the paraffins in the blending component by contacting said component under reforming conditions with hydrogen in the presence of a catalyst comprising a noble metal on magnnesium oxide in an alumina gel matrix, to obtain a cyclized blending component, and (2) catalytically reforming said cyclized blending component in the presence of a conventional platinum or platinum bi-metallic reforming catalyst of an alumina or alumina containing support.

2. A process according to claim 1 in which the noble metal is platinum.

3. A process according to claim 1 in which the noble metal is palladium.

4. A process according to claim 2 in which magnesium oxide is impregnated with a solution of a soluble platinum compound and the impregnated powder is dried prior to its mixing into the alumina gel matrix.

5. A process according to claim 4 in which the platinum compound is chloroplatinic acid.

6. A process according to claim 1 in which the noble Cyclized Raffinate Charge stock properties APl gravity 59.6 56.0 ASTM pct. point. F. 276. 266. Aromatics. vol. pct. l 1.8 20.1 Naphthenes. vol. pct. 7.7 19.7 Potential aromatics. wt. pct. 21.5 42.4 Average mol wt. 122. 116. Yields basis FF Wt. Pct. SCFB Wt. Pct. SCFB Hydrogen 0.56 273.15 0.90 450.75 Methane 2.58 158.12 1.62 101.14 Ethane 2.82 92.31 1.77 59.04 Propane 6.41 142.89 4.02 91.39 Total dry gas. (C -C 11.82 393.33 7.41 251.59 Wt. Pct. Vol. Pct. Wt. Pct. Vol. Pct. lsobutane 4.59 6.04 2.94 3.94 Normal butane 6.39 8.11 4.09 5.29 Total butanes 10.99 14.15 7.04 9.24 lsopentane 7.26 8.60 4.65 5.62 Normal pentane 3.17 3.72 2.03 2.43 Total pentanes 10.44 12.33 6.69 8.05 Depentanized liq. 66.17 63.85 77.93 75.15 Total (vol. C.,+) 100.00 90.34 100.00 92.45 DB liquid data yield 76.62 76.18 84.63 83.21 API gravity 58.5 52.8 Octanes Clear +3cc tel. Clear +3cc tel. Research 90.0 98.1 90.0 98.3 Motor 80.9 88.9 81.1 89.2

These data show that the step of cyclizing the paraffinic gasoline components is extremely effective in increasing the overall depentanized liquid yield when upgrading the octane number. Although the octane number of the raw raffinate can be increased to 90 RON clear without the cyclization step, the liquid yield is much lower 76.1 vol.% as against 83.2 vol.% for the cyclized raffinate. Also of significance is the higher hydrogen yield when processing the precyclized raffinate.

What is claimed is:

l. A process for increasing the octane number of a paraffin containing gasoline blending component boiling within the gasoline boiling range and having a parmetal is stabilized with another metal selected from Groups IV A, V B, Vl B, V11 B and VIII of the Periodic Table.

7. A process according to claim 1 in which the catalyst of step (1) is promoted with a halogen compound.

8. A process according to claim 1 in which the contacting takes place at a temperature of from about 500 to about 1,100F. and a pressure of from about 50 to about 900 p.s.i.g.

9. A process according to claim 8 in which the temperature is from 700 to l,000F. and the pressure is 

1. A PROCESS FOR INCREASING THE OCTANE NUMBER OF A PARAFFIN CONTAINING GASOLINE BLENDING COMPONENT BOILING WITHIN THE GASOLINE BOILING RANGE AND HAVING A PARAFFIN CONTENT OF FROM ABOUT 70 PERCENT OR HIGHER WHICH COMPRISES THE STEPS OF (1) CYCLIZING THE PARAFFINS IN THE BLENDING COMPONENT BY CONTACTING SAID COMOONENT UNDER REFORMING CONDITIONS WITH HYDROGEN IN THE PRESENCE OF A CATALYST COMPRISING A NOBLE METAL ON MAGNNESIUM OXIDE IN AN ALUMINA GEL MATRIX, TO OBTAIN A CYCLIZED BLENDING COMPONENT, AND (2) CATALYTICALLY REFORMING SAID CYCLIZED BLENDING COMPONENT IN THE PRESENCE OF A CONVENTIONAL PLATINUM OR PLATINUM BI-METALLIC REFORMING CATALYST OF AN ALUMINA OR ALUMINA CONTAINING SUPPORT.
 2. A process according to claim 1 in which the noble metal is platinum.
 3. A process according to claim 1 in which the noble metal is palladium.
 4. A process according to claim 2 in which magnesium oxide is impregnated with a solution of a soluble platinum compound and the impregnated powder is dried prior to its mixing into the alumina gel matrix.
 5. A process according to claim 4 in which the platinum compound is chloroplatinic acid.
 6. A process according to claim 1 in which the noble metal is stabilized with another metal selected from Groups IV A, V B, VI B, VII B and VIII of the Periodic Table.
 7. A process according to claim 1 in which the catalyst of step (1) is promoted with a halogen compound.
 8. A process according to claim 1 in which the contacting takes place at a temperature of from about 500* to about 1,100*F. and a pressure of from about 50 to about 900 p.s.i.g.
 9. A process according to claim 8 in which the temperature is from 700* to 1,000*F. and the pressure is from 50-500 p.s.i.g. 